The present invention relates to a back lid of a camera, and more particularly to a back lid with a pressure plate which can hold film flat.
It is known in the art to use an integrally formed plastic camera body and a back lid, which have the advantages of lightening weight and reducing manufacturing cost. This plastic camera body is generally box-shaped, which gives it sufficient strength. However, the back is plate-shaped and tends to be insufficient in strength and to be deformed upon applying an external force thereto.
The back lid is provided with a pressure plate for pressing film loaded in a camera to hold it flat. As the pressure plate is to be press resiliently the film from the rear, the pressure plate is provided with resiliently deformable members such as leaf springs which at their ends are fixed to the camera back lid, so that they are slightly resiliently deformably movable lengthwise.
Even though there are resiliently deformable members between the pressure plate and the integrally formed plastic back lid, the pressure applied by the pressure plate is apt to be distributed unevenly over the film when the back lid is deformed, making it difficult to hold the film flat. For eliminating this difficulty, it would suffice from a structural standpoint to provide a supplemental reinforcing frame member fixed to the back lid. But this would result in an increased number of parts, disadvantageous assembly operations, and increased manufacturing cost.
On the other hand, the conventional pressure plate, as described above, has a structure which makes it difficult to decrease the number of parts and to simplify its assembly operations.
From the point of view of economy, the resiliently deformable members can be formed as leaf springs integral with the pressure plate, from a single metal plate. But in this case, the single metal plate must be thin enough to provide the leaf springs with a suitable resilient deformability. However, a thin metal plate is unable to provide the pressure plate with the rigidity necessary to maintain the film optically flat. A pressure plate integral with the leaf springs, therefore, is technically impractical.
Integrally formed plastic pressure plates, provided instead of the aforementioned metal pressure plate, also have serious problems in that it is hard not only to maintain the leaf springs with a constant resiliency but also to give them a proper and sufficient strength. An additional problem is that such an integrally formed plastic pressure plate is apt to be deformed non-resiliently by repeated use.